1. Field of the Invention
This invention relates to a method for the production of ceramics reinforced with three-dimensional fibers and an apparatus for the production of the ceramics.
2. Description of the Background
Ceramics reinforced with fibers have recently been attracting attention as products improved by elimination of such drawbacks as low toughness and poor reliability of strength which are monolithic ceramics. Three kinds of fiber reinforcing type are known: one-dimensional reinforcement in which fibers are laid out only in one direction, two-dimensional reinforcement in which fibers are laid out in two directions (in a plane), and three-dimensional reinforcement in which fibers are laid out in three directions (in a cubic pattern). These kinds of fiber reinforcement manifest the following characteristics.
The one-dimensional fiber reinforcing type manifest tensile and flexural strength sufficiently in the direction of the fibers but only meagerly in directions at or near perpendicular to the direction of the fiber reinforcement. The two-dimensional fiber reinforcing type exhibits great strength in the plane containing the fibers but poor strength in the direction perpendicular to the plane. They also tend to induce peeling. In contrast, the three dimensional fiber reinforcing type shows strength virtually uniformly in an isotropic manner in all directions. The three-dimensional fiber reinforcing type is therefore ideal for the purpose of reinforcement.
While fiber-reinforced ceramics using one-dimensional and two-dimensional fiber reinforcements can be manufactured rather easily, those using three-dimensional fibers cannot.
Basically, the ceramics reinforced with three-dimensional fibers (hereinafter referred to as "three-dimensional fiber-reinforced ceramics") have a construction comprising a three-dimensionally formed fibrous web (preform) and a ceramic mass filling the interstices between the component fibers of the fibrous web to give rise to a matrix. Since the three-dimensional fibrous preform, unlike the one-dimensional and two-dimensional fibrous preforms, has component fibers densely and cubically interwoven, the individual fibers thereof strongly contact one another and form narrow interstices and not all of the gaps between the adjacent fibers are interconnected. Thus, the three-dimensional fibrous preform is not easily filled with a matrix substance.
The filling of the three-dimensional fibrous preform with the matrix substance is generally effected by mixing the matrix substance with such additives as an organic binding agent to form a liquid substance, injecting this liquid substance into a preform, and then firing the resultant composite. In this case, the organic binding agent and other additives contained in the liquid substance filling the preform induce thermal decomposition and the like and, as illustrated in FIG. 1, give rise to many pores 4 in a matrix part 3. For the purpose of producing ceramics which are reinforced with densely interwoven three-dimensional fibers, therefore, it is necessary that the number of such pores in the composite should be decreased to the fullest possible extent.
This invention has for its object the provision of an improved method for the production of ceramics reinforced with three-dimensional fibers and an apparatus for working this method.